Communications networks, that dispatch and collect data from a central location to a large number of geographically dispersed facilities, can be implemented by guided lines, i.e., wireline, or by transmission through the air, such as by radio, optical or infra red waves. There is an increasing need for highly reliable, low cost methods to provide such data communications facilities particularly along roadways. Current communications options include wireline, or fiberline, and broadcasted radio. However, pole facilities and duct space for wirelines are increasingly difficult to obtain and broadcast radio is limited by increasing interference and limited spectral capability.
Reliability in a communications system is usually achieved by having duplicate facilities and by an alternate routing capability. Both methods are costly.
Microwave, infra red or optical links often require expensive towers to obtain suitable line-of-sight clearance. Party line communications along right of ways, such as roadways, are prone to serious reliability problems. Simplex communications links which require the least equipment and facility suffer the potential for major failures and inflexibilities. Failures in complex communications networks occur randomly, often in unanticipated patterns caused by equipment failure, human error, facility destruction, sabotage, etc. All of these factors are considerations in the design of data collection and distribution systems.